Archiving

archive_mode

Parameter description: Specifies whether to archive WALs.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

NOTICE:

When wal_level is set to minimal, the archive_mode parameter is unavailable.

Value range: Boolean

• on indicates that the archiving is enabled.
• off indicates that the archiving is disabled.

Default value: off

archive_command

Parameter description: Specifies the command set by the administrator to archive WALs. You are advised to set the archive log path to an absolute path.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

NOTICE:

• If both archive_dest and archive_commandare configured, WALs are preferentially saved to the directory specified by archive_dest. The command configured by archive_commanddoes not take effect.

• Any %p in the string is replaced by the absolute path of the file to archive, and any %f is replaced by only the file name. (The relative path is relative to the data directory.) Use %% to embed an actual % character in the command.

• This command returns zero only if it succeeds. The following shows the command:

archive_command = 'cp --remove-destination %p /mnt/server/archivedir/%f'

• --remove-destination indicates that files will be overwritten during the archiving.

• If there are multiple archive commands, write them to the shell script file and set archive_commandto the command for executing the script. For example:

  -- Assume that multiple commands are as follows:
  test ! -f dir/%f && cp %p dir/%f
  -- The content of the test.sh script is as follows:
  test ! -f dir/$2 && cp $1 dir/$2
  -- The archive command is as follows:
  archive_command='sh dir/test.sh %p %f'

Value range: a string

Default value: (disabled)

archive_dest

Parameter description: Specifies the path set by the administrator to archive WALs. You are advised to set the archive log path to an absolute path.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

NOTICE:

• If both archive_dest and archive_commandare configured, WALs are preferentially saved to the directory specified by archive_dest. The command configured by archive_commanddoes not take effect.
• If the string is a relative path, it is relative to the data directory. The following is an example:

archive_dest = '/mnt/server/archivedir/'

Value range: a string

Default value: an empty string

archive_timeout

Parameter description: Specifies the archiving period.

archive_timeout is suitable for scenarios where active-standby streaming replication is not used or where WAL logs need to be archived. By default, file switching will occur when WAL reaches a certain size, and archiving can copy WAL files at this time. When the system is idle, some WAL logs may remain in the memory and cannot be archived in time. After archive_timeout is set to greater than 0, the system will force the WAL content in the memory to be flushed to the disk when the set value is exceeded to achieve timely archiving of WAL logs.

This parameter is a SIGHUP parameter. Set it based on instructions provided in Table 1 GUC parameters.

NOTICE:

• The server is forced to switch to a new WAL segment file when the period specified by this parameter has elapsed since the last file switch.
• Archived files that are closed early due to a forced switch are still of the same length as full files. Therefore, a very short archive_timeout will bloat the archive storage. You are advised to set archive_timeout to 60s.

Value range: an integer ranging from 0 to INT_MAX. The unit is second. 0 indicates that archiving timeout is disabled.

Default value: 0